Recent advances in speech synthesizing techniques and an increase in the storage capacity of storage devices provided in speech output equipment have made it possible to synthesize speech of a variety of qualities. Speech synthesis has been used heretofore for the purpose of providing a user with information or warnings by equipping a speech output unit with an information processor or the like for synthesizing speech.
With the conventional method set forth above, however, a problem is encountered. Specifically, when a plurality of devices (speech output units) each having a speech synthesizing function are present in a certain space and the user is presented with information such as an alert using synthesized speech that is output from each of these speech output units, it is difficult for the user to determine which device has synthesized and output the speech.